Engagement occurs when students are inherently eager to pursue a course. Many factors might influence student engagement. From a sociocultural perspective, one such factor might be the classroom social environment. From this point of view, the purpose of this study is to investigate the relationships between student engagement, school social climate, classroom social environment, loneliness, attitudes toward English course, attitudes toward the school and the grade point average. The instrument includes the scales of classroom engagement, school social climate, perceptions of classroom social environment, short form of the UCLA loneliness, attitudes toward English course and school. The data were collected from 734 high school students of 9, 10, 11 and 12th grades in 2015-16. The results indicated that perceptions of classroom social environment, attitudes toward English course, school social climate and grade point average significantly predicted student engagement. Furthermore, perceptions of classroom social environment explained the highest proportion of variance in student engagement.